The invention relates to a multifunctional valve for a vehicle tank having the features of the preamble of patent claim 1.
An appropriate valve has already been disclosed, which valve can be mounted in the cover of a vehicle tank and combines at least the following functions in one sub-assembly:
Ventilating the tank as it is being filled and protecting it against overfilling by building up a counter pressure,
Aeration while fuel is being removed during operation,
Protecting the tank against overload in the event of an excessive build up of pressure,
Closing in the event of the vehicle taking up an excessive sloping position or rolling over.
As a fuel tank is being filled, the flowing fuel causes a mixture of air and fuel vapors to be displaced. This mixture initially flows through a large ventilation opening to an activated carbon filter which retains the fuel parts and allows essentially purified air to pass into the surroundings. In the case of the known valve, said, large ventilation opening is assigned a flap which, on the one hand, is pretensioned resiliently into its closing position but, on the other hand, is held open by a buoyancy body in the normal position of the vehicle. As filling increases, the buoyancy body, whose density (1.2) is clearly higher than that of the fuel (0.7), becomes more and more submerged in the fuel. The volumetric buoyancy of the buoyancy body alone causes the force ratio between its own effective weight and the force of the abovementioned closing spring to change, with the result that said closing spring closes the flap before the level of the tank has reached its maximum height.
Parallel in liquid terms to the large opening, the valve is furthermore provided with an additional, substantially smaller opening which likewise serves for ventilation during operation, i.e. for the escape of fuel vapors as pressure is building up in the tank during the journey or while the vehicle is at a standstill. This small opening has also to be closed if there is a further rise in the fuel so that no liquid fuel can get into the ventilation duct. The opening is therefore assigned a valve body which is likewise pretensioned into the closing position with a relatively weak spring and is held open by the weight of a buoyancy body (density likewise greater than the fuel density). The small opening is then finally also to be closed according to the same principle as in the case of the large opening. For safe operation of the tank it is important for a gas pocket always to be maintained above the liquid fuel as a buffer for pressure fluctuations.
In conjunction with the springs, the high density of the buoyancy bodies ensures that the two openings are securely closed in the event of the vehicle taking up an excessive sloping position or rolling over, because the weight or descending force of the buoyancy bodies is then added to the respective closing spring force. If the buoyancy bodies were designed in the specified configuration as floats, in the event of the vehicle rolling over they would lift the flap or the valve body off from the opening cross-sections counter to the spring force, with the result that the tank would not be sealed at these openings.
In the case of the known valve, however, very hesitant filling of the tank may finally also cause the gas pocket above the liquid level to be completely dissipated via the small aeration opening and the tank to be completely filled with liquid. In particular, the valve body closes only at an already very high level, the assumption obviously having been made from this that a sufficient counter pressure has already been built up in the tank due to the throttle resistance of the small opening. This may result in the tank being overfilled.
Furthermore, the second opening is arranged to one side of the larger, first opening, with the result that the sub-assembly which is inserted in the form of a cover into a recess in the tank cover, altogether needs a relatively large amount of space.
However, with regard to reliable sealing, the aim is to keep such recesses as small as possible.
Finally, the sub-assembly furthermore comprises a pressure relief valve which should protect the tank against damage in the event of a sharp rise in pressure. This essentially comes into operation whenever the temperature of the fuel in a full tank sharply rises and the pressure of the abovementioned gas pocket rises beyond the threshold value of the pressure relief valve. However, in the case of a tank which has already been overfilled, liquid fuel may also emerge.
An aeration and roll-over valve has also been disclosed, this valve comprising a bell-shaped float having a closing body, in whose downwardly open interior is maintained a gas pocket, in the event of the tank level rising, while the aeration flow may pass by the float on the outside. A ball is provided below the float, which ball in the event of a sloping or roll-over position prevails over the lifting force of the float and keeps the closing body in the closing position. A second overflow opening is not provided in this valve.
The invention is based on the object of improving a valve of the generic type.
This object is achieved according to the invention by the defining features of patent claim 1. The features of the subclaims specify advantageous developments of this subject matter.
If the two openings can each be closed by floats bearing closing bodies, reliable closing as the liquid level rises is initially achieved therewith. For the event of rolling over, which occurs rarely, a dedicated, mechanical actuating device is provided which counteracts the buoyancy of the floats in this extreme situation, with the result that the openings can be securely closed against fuel emerging.
In a manner known per se, the actuating device may comprise at least one body whose weight is greater than the lifting force of the float bodies, and may thus apply a particularly simple solution. However, it may also comprise a further float, a deflection mechanism being connected to the further float, which mechanism transmits the lifting force of the further float, in the event of rolling over, to the two float bodies to counter their lifting force.
In each case, it is particularly advantageous if the two float bodies are jointly retained by a single device in the closing position of their assigned closing bodies. This in turn may be achieved in a particularly space-saving manner if the two openings and the floats are assigned coaxially to one another.
The second opening may be provided in a space-saving manner in the first float body if the latter is, for example, of bell-shaped design and forms a guide for the second float body. This also fulfills the requirement for the entire valve to have a lateral extent which is as small as possible.
Delayed closure of the second opening can be effectively ensured by the second float being lifted up more slowly than the first one. This is achieved, for example by the second float being manufactured from a material of a somewhat higher density.
Again in a space-saving manner, the two float bodies may be guided in a cup-shaped guide which has a conical or concavely curved bottom and the interior of which communicates with the container by liquid. The shape of the bottom then forms the rolling guide for the abovementioned weight body for closing the two ventilation openings.
The roll-over action is particularly functionally reliable, even over prolonged periods of use, if a ball is arranged between the bottom and the lower side of the float bodies, the diameter of which ball is matched to the bottom and to the distance of the lower side of the float bodies from the bottom in a manner such that the two closing bodies are brought mechanically into the closing position before the ball moves laterally to bear against the guide. This reliably avoids the ball jamming and also undesirable development of noise. As the ball is constantly wetted by fuel as it rolls along the downwardly curved bottom, the friction between its surface and the lower side of the float body is also negligible.
A float valve is thus available which allows the tank to be aerated and ventilated, protects the tank against excessive pressure and overfilling, has a submerged tube switch-off (build-up of a sufficient counter pressure as the tank is being filled to automatically switch the fuel nozzle off after the permissible level is reached) and includes a roll-over action.
The valve consists of a double float (external and internal floats), which floats, depending on the level, successively close the filling and operating vents and open them again as the level drops.
A roll-over ball is arranged below the floats, which ball, in the event of the tank being in any sloping or roll-over position, overcomes the lifting forces of the floats and closes the valve.
Further ventilation is not provided.
Further details and advantages of the subject matter of the invention emerge from the drawing of an exemplary embodiment and the subsequent, detailed description thereof in the following.